<!--
 * @Author: xinyang3
 * @Date: 2021-03-05 03:34
 * @Descripttion: awesome description
 * @LastEditors: xinyang3
 * @LastEditTime: 2021-03-05 04:08
-->
<html>

<head>
  <title>scroll</title>
  <style type="text/css">
    .top {
      background-color: coral;
      height: 300px;
      width: 800px;
      margin: 0 auto;
    }

    .elem {
      width: 300px;
      margin: 0 auto;
      text-align: center;
    }
    .middle {
      height: 200px;
      background: blue; 
      overflow: auto;
    }

    .inner {
      height: 800px;
      background: orange;
    }
  </style>
</head>

<body>
  <div class="top"></div>
  <div class="middle">
    <div class="inner"></div>
  </div>
  <div class="hidden"></div>
  <button class="test1">test1</button>
  <script src="./jquery-3.6.0.js"></script>
  <script src="./index.js"></script>
</body>

</html>